The present invention relates to a semiconductor device and a method of fabricating the same.
Recently, in the formation of a multilayered interconnection, a method which uses a low-dielectric-constant film having a relative dielectric constant lower than that of a silicon oxide (SiO2) film as an interlayer dielectric film is proposed, in order to reduce the wiring delay. An example of this low-dielectric-constant film is an SiOC film formed by doping substantially 10 to 20% of carbon into a silicon oxide (SiO2) film.
Unfortunately, this low-dielectric-constant film has low strength and cracks during processing, causing various inconveniences in the formation of a multilayered interconnection. Therefore, a protective film which protects the low-dielectric-constant film is formed on it.
Also, since the low-dielectric-constant film contains carbon, the adhesion between the low-dielectric-constant film and its protective film is low. Therefore, high adhesion between the low-dielectric-constant film and protective film is ensured by lowering the carbon concentration near the surface of the low-dielectric-constant film before the protective film is formed.
In addition, when the protective film is to be formed by using plasma CVD (Chemical Vapor Deposition), the carbon concentration near the surface of the low-dielectric-constant film is lowered.
Although the low-dielectric-constant film is originally hydrophobic, the surface and vicinity change to have hydrophilic nature because the carbon concentration lowers.
Accordingly, the low-carbon-concentration region near the surface of the low-dielectric-constant film readily adsorbs OH and water (H2O). As a consequence, the effective relative dielectric constant rises, or a process gas remaining in the low-dielectric-constant film is eliminated during the process to cause film peeling or metal corrosion.
A reference concerning the carbon concentration near the surface of the low-dielectric-constant film is as follows.
Japanese Patent Laid-Open No. 2003-17561